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Search Publications by: Angela R. Hight Walker (Fed)

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Displaying 126 - 150 of 184

Probing the Growth and Aging of Colloidal Cobalt Nanoparticles

June 11, 2009
Author(s)
Guangjun Cheng, Cindi L. Dennis, Robert D. Shull, Angela R. Hight Walker
We have combined transmission electron microscopy (TEM) and magnetic measurements to characterize the growth of colloidal cobalt (Co) nanoparticles during synthesis and their subsequent stability in air. During the growth, TEM measurements have shown the

Dipolar Chains formed by synthesized cobalt nanocubes

May 11, 2009
Author(s)
Guangjun Cheng, Robert D. Shull, Angela R. Hight Walker
Cobalt nanocubes with an average edge length of 50 nm and the epsilon crystalline structure were synthesized via thermo-decomposition in 1,2-dichlorobenzene at 120 oC in the presence of the surfactants. These nanocubes form dipolar chains upon drying in

Centrifugal Length Separation of Carbon Nanotubes

October 1, 2008
Author(s)
Jeffrey A. Fagan, Matthew Becker, Jae H. Chun, Barry J. Bauer, Jeffrey R. Simpson, Angela R. Hight Walker, Erik K. Hobbie
Separation of single wall carbon nanotubes (SWCNTs) by length via centrifugation in a high density medium, and the characterization of both the separated fractions and the centrifugation process are presented. Significant quantities of the separated SWCNTs

Surface-Enhanced Raman Spectroscopy via Gold Nanostars

September 28, 2008
Author(s)
Emren Nalbant-Esenturk, Angela R. Hight Walker
Anisotropic metallic nanoparticles have unique optical properties, which lend them to applications such as Surface Enhanced Raman Spectroscopy (SERS). Branched and star-shaped gold nanoparticles have been prepared in aqueous phase by seed-mediated growth

Influence of the Colloidal Environment on the Magnetic Behavior of Cobalt Nanoparticles

November 6, 2007
Author(s)
Guangjun Cheng, Cindi L. Dennis, Robert D. Shull, Angela R. Hight Walker
The magnetic properties of 10 nm cobalt (Co) nanoparticles in 1,2-dicholorbenenze (DCB) are investigated via a series of magnetization (M) vs. temperature (T) measurements. A rapid rise in magnetization around 250 K during warming and a sudden drop at 240

Synthesis and Characterization of Cobalt/Gold Bimetallic Nanoparticles

April 1, 2007
Author(s)
Guangjun Cheng, Angela R. Hight Walker
Cobalt/gold (Co/Au) bimetallic nanoparticles are prepared by synthesizing Au via chemical reduction in the presence of pre-synthesized Co nanoparticles. Transmission electron microscopy (TEM), ultraviolet-visible (UV-vis) absorption spectrometry, and a

Comparative Measures of Single Wall Carbon Nanotube Dispersion

September 14, 2006
Author(s)
Jeffrey A. Fagan, Brian Landi, Idan Mandelbaum, Vardhan Bajpai, Barry J. Bauer, Kalman D. Migler, Jeffrey R. Simpson, Angela R. Hight Walker, Ryan Raffaelle, Erik K. Hobbie
Model polymer composites of DNA wrapped single-wall carbon nanotubes (SWNTs) dispersed in polyacrylic acid are used for a systematic comparison of the different metrologies currently used to evaluate SWNT dispersion. Application of a pH-controlled

Method for Measuring the Raman Gain Tensor in Optical Fiber

April 7, 2006
Author(s)
Idan Mandelbaum, M Bolshtyansky, T F. Heinz, Angela R. Hight Walker
In this paper we introduce a technique to measure the tensor properties of the Raman gain in a short piece (10m) of silica based polarization maintaining optical fiber. We present the results of the measurement and show agreement with new and previous bulk

Quantitative, Interactive Measurement of Tissue Engineering Scaffold Structure Using Immersive Visualization

January 1, 2006
Author(s)
Jeffrey Fagan, Erik K. Hobbie, Brian Landi, Idan Mandelbaum, Vardhan Bajpai, Barry J. Bauer, Kalman D. Migler, Jeffrey R. Simpson, Angela R. Hight Walker, Ryan Raffaelle
At NIST, we are using new approaches to better understand and quantify the structure of tissue engineering scaffolds. This approach uses immersive visualization (IV) and is inherently three dimensional, multivariate and interactive, providing real-time

Rotational Spectra, Conformational Structures and Dipole Moments of Thiodiglycol by Jet-Cooled FTMW and Ab Initio Calculations

May 1, 2004
Author(s)
L H. Xu, Q Liu, R D. Suenram, Francis J. Lovas, Angela R. Hight Walker, J O. Jensen, A C. Samuels
The rotational spectra of three low-energy conformers of thiodiglycol (TDG) (HOCH2CH2SCH2CH2OH) have been measured in a molecular beam using a pulsed-nozzle Fourier-transform microwave spectrometer. To determine the likely conformational structures with ab

Rotational Spectra of the Diastereomers of Soman

April 1, 2004
Author(s)
R D. Suenram, R S. DaBell, Angela R. Hight Walker, D J. Lavrich, David F. Plusquellic, M W. Ellzy, J M. Lochner, L Cash, J O. Jensen, A C. Samuels
The pure rotational spectrum of the nerve agent Soman has been recorded and assigned using a pulsed molecular beam Fourier transform microwave spectrometer. The spectrum consists of transitions from two different isomers that are likely the [SS] (or [RR])

Continuous-Wave Terahertz Spectroscopy of Plasmas and Biomolecules

March 1, 2004
Author(s)
David F. Plusquellic, T M. Korter, Gerald T. Fraser, R J. Lavrich, Eric C. Benck, C R. Bucher, Angela R. Hight Walker, J L. Domenech
Continuous-wave linear-absorption spectroscopy based on THz radiation generated by solid-state photomixers has been applied to the investigation of the dynamics of biomolecules in polyethylene matrices and to line shape studies of HF for diagnostics of

Surface Enhanced Raman Spectroscopy in a Microfluidic Device

February 1, 2004
Author(s)
D Dunmire, D B. Romero, Guangjun Cheng, Angela R. Hight Walker
Surface enhanced Raman spectroscopy (SERS) is employed to study the solution phase vibrational structure of molecules on gold and silver colloids. Gold and silver colloids show large enhancement factors enabling sub-micromolar detection limits. Using a

Synthesis of Bioconjugated Magnetic Nanoparticles for Magneto-Raman Study

February 1, 2004
Author(s)
Guangjun Cheng, D B. Romero, D Dunmire, Angela R. Hight Walker
We are investigating the effects of an externally applied magnetic field on the structure and magnetic properties of biomolecules (DNA and proteins). A newly constructed, magneto-Raman confocal microscope system couples a cryo-magnet to a triple grating
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